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Author Topic: Camera calibration improving accuracy?  (Read 18684 times)

bigben

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Re: Camera calibration improving accuracy?
« Reply #15 on: April 29, 2015, 02:49:34 PM »
Having more points isn't really relevant compared to having real world reference points to align those to.  In theory it shouldn't make any difference what size the reference target is. The other important thing is that the reference points chosen should occur across the field of view.

To do a similar approach in the Pro version you could specify a large grid of GCPs across a wall and use the standard align and optimise steps.  The standard version doesn't use GCPs, making the lens calibration tool more practical for those users.

Advice to take multiple photographs of the same view at different rotation angles (e.g. http://culturalheritageimaging.org/Technologies/Photogrammetry/) is geared towards providing the image data that increases the likelihood of the optimisation process arriving at accurate values in the absence of calibrated values
« Last Edit: May 01, 2015, 12:06:08 AM by bigben »

aggieair

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Re: Camera calibration improving accuracy?
« Reply #16 on: April 30, 2015, 09:13:16 PM »
I calibrate our cameras in-house using the big dot wall.  I ran it both ways - with my camera info and letting Agisoft pick the interior orientation values.  Entering the camera calibration file into an Agisoft project and it did not improve the error results.  In fact, it was less accurate by 0.03 m (in the Error M and Error Pix columns).  I didn't do an accuracy assessment in ArcGIS though.  Letting Agisoft pick the interior orientation info was slightly better in the end. 

The only time I'd use that camera calibration info is if I created my mosaic in EnsoMosaic which needs it.

Someone asked me why I thought my calibrated camera info would improve results (I don't know it just seems like knowing exact data would be ideal, no?), but I was surprised.

bigben

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Re: Camera calibration improving accuracy?
« Reply #17 on: May 02, 2015, 12:11:36 AM »
The other thing to consider is that if your have calibrated lens parameters, then using any other values is technically distorting your images.  Optimising these after alignment may produce a cleaner result BUT you are altering your images to fit the data. A small deviation may be acceptable, but you have no control over that process.